Carrera 3.2 engine sound, thoughts?

[Roger 911]

Originally Posted by gomezoneill

" I put 5w-30 mineral oil in." WHAT?

Have you ever looked at 20w-50 mineral oil at 10 deg F? It looks like STP oil treatment, e.g., honey. Read the whole post.

[gomezoneill]

Oh I thought you meant the mineral oil people use as a laxative. Sorry.

[nene]

Hahaha, I thought so too!

[Roger 911]

I just wanted to close the loop on this thread. It turned out the sound was a result of excessive cam and rocker wear caused by a blocked spray bar in the cam tower. The cam restrictor had some reddish black flakes (non metallic) blocking the orifice that feeds the oiling bar. My hunch is that these flakes came from the oil tank.

[gomezoneill]

CRAP!!!! That's to bad. It's strange that you drained the tank and said it was clean. none of those flecks were in the oil you drained? Seems odd. Are you sure it's not dried out gasket that broke up into pieces from somewhere in the motor?

[Roger 911]

Originally Posted by gomezoneill

CRAP!!!! That's to bad. It's strange that you drained the tank and said it was clean. none of those flecks were in the oil you drained? Seems odd. Are you sure it's not dried out gasket that broke up into pieces from somewhere in the motor?

Here's my theory. I installed this motor back in 2012. At the same time, I also installed a front mounted oil cooler. I utilized the factory 1972 configuration. This included removing a plug from the bottom of my oil tank for the return line from the front cooler. The tank had 40 years of petroleum deposit at that time. I suspect some of the deposits were broken loose when I removed the plug and attached the new line. I also had to remove and reinstall a couple oil lines on the top of the tank. When I started the car up, these flakes were sucked into the motor. They seem to have found a home in the came oil restrictor (the reduced size, 964 turbo variety), especially the left one. It must not have totally blocked oil flow. because the motor ran great for eight years and 15K miles, including probably a half dozen HPDE events along the way. But there wasn't enough oil flowing through to properly lubricate the cam lobes, especially by the time it got back to #3. A couple years ago, I started to really notice the noisy valves. I chalked it up to poor valve adjusting on my part. But as we can see, it wasn't my valve adjusting prowess that was the problem.

[gomezoneill]

Is the cam shot too?

[Roger 911]

Originally Posted by gomezoneill

Is the cam shot too?

Oh yes. Don't have a photo handy, but the lobe has flat spots on it, like a trapezoid. I've never seen anything like it. New billet Webcam 20/21s are on order, along with new rocker arms.

[cmcfaul]

That looks nasty.

Chris

[Hx911]

thank you for making the effort and post your findings!

[mikedsilva]

wow, glad you got it sorted.

[gomezoneill]

You sure are calm about it (from what I can tell) I'd be loosing my mind.
Are you going to do a complete tear down to check the bearings etc?

[Roger 911]

Originally Posted by gomezoneill

You sure are calm about it (from what I can tell) I'd be loosing my mind.
Are you going to do a complete tear down to check the bearings etc?

I was actually somewhat relieved to figure out what the problem was. I've been playing with air cooled 911s since 1998. I have a reasonably good sense of how they work, and how they should sound. This sound over the last couple years sounded like noisy valves, but I could not get rid of it. I couldn't find broken springs, or evidence of worn guides, and then you start to think about bigger issues. So once I discovered what it was, I felt better.

Sure, you can make an argument for tearing it all down. However, as I stated in previous posts, the car ran great, good oil pressure, no other weird noises or smoking, no broken head studs, etc. I'm not an expert, but my gut tells me that the rest of the motor is OK (for now!). Pulling the engine and replacing cams is significantly less work and expense, than doing a full rebuild. I'm comfortable taking that risk, i.e., not doing a full rebuild.

[gomezoneill]

You may want to take off your oil filter and cut it open to check for captured particles. You have to pull the motor and take the cam housing off it anyway it would be a shame if there were issues with the lower end. All that metal that was ground off the rockers and cam had to go somewhere.

[Roger 911]

Yes, I do plan to cut open the filter. However, I have changed the oil over a dozen times since the motor was installed. So if these flakes are petroleum deposits from the oil tank, any evidence in the filter is probably long gone. Also, every time I change the oil, I always inspect the oil and the magnetic plugs carefully. I have never seen anything in the oil, and the plugs have only shown the normal fine metal dust.

The motor is already out. Fortunately you don't have to remove the cam towers to replace the cams.

[Roger 911]

I'm thinking about installing an inline oil pre-filter in the feed line between the oil tank and the motor, like this in 16AN ;



This should prevent any similar problems in the future. Anyone out there have any experience with screening/filtering oil on the feed side of the system?

[gomezoneill]

Will that restrict the flow at all?

[Roger 911]

Originally Posted by gomezoneill

Will that restrict the flow at all?

I don't think so. It's not really a filter. It has a metal screen that filters out particles larger than 140 microns. Versus an oil filter which I believe is in 5-10 micron range. Unfortunately, with the 1972 oil tank and lines, I'm not really sure I can even fit this in there.